1. Field of the Invention
This invention relates to a mechanism for producing stitched patterns in a zigzag sewing machine, and more particularly to an engaging mechanism of a plurality of followers which follow 1st and 2nd pattern cams to be rotated at different speed reduction ratios respectively.
Conventional zigzag sewing machines are in general designed with respect to sizes of machine frames, and accordingly spaces within the machine frames are limited. Therefore, pattern forming cams are selected in size, especially diameter, irrespectively of exchanging type or built-in type. In addition, cam lifts and cam pressing angles are selected so that cam followers are movable, and therefore the number of swinging movements of a needle bar during one rotation of the pattern forming cam is naturally limited, and the stitching number during one cycle of a pattern cannot be increased as desired. Therefore the cams with a maximal reduction ratio 1:18 are utilized.
It has been recently desired to stitch patterns of larger sizes such as satin stitches, scallop stitches. Speed reduction cams of ratio 1/36 are partially incorporated for producing patterns of 36 stitches in one cycle as far as scallop stitches are concerned. However, the cam lift in response to the pressure of the cam follower is limited as mentioned above, and it has been difficult to swing the needle in the full amplitude amount (e.g. 7 mm) of the zigzag sewing machine. Accordingly, patterns to be produced have been limited.